Brass alloy

ABSTRACT

A brass alloy is formed from 54 to 64% Cu, 0.05 to 0.15% Al, 0.005 to 0.5% In, at least one of the components of Fe, Sn and Ni in an amount of 0.01 to 3.0%, balance Zn and also unavoidable impurities. The combination of these materials provides a brass alloy that has improved machinability.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation, under 35 U.S.C. § 120, of copendingInternational Patent Application PCT/EP2022/053611, filed Feb. 15, 2022,which designated the United States; this application also claims thepriority, under 35 U.S.C. § 119, of German Patent Application DE 10 2021103 686.0, filed Feb. 17, 2021; the prior applications are herewithincorporated by reference in their entireties.

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a brass alloy. It relates more particularly toa brass alloy to which neither lead (Pb) nor bismuth (Bi) have beenadded.

One such brass alloy is known from European patent EP 3 320 122 B1. Theknown brass alloy consists of 54 to 64% Cu and 36 to 46% Zn, and thealloy has an In content of 0.005 to 1.0% and an addition of at least oneof the components Fe, Sn, Ni or Mn of together 0.01 to 3.0%. No Bi isadded to the alloy.

In the past, the machinability of brass alloys was improved by adding Pbto an extent of up to 4 wt %. The addition of Pb is greatly restrictedowing to statutory stipulations, according to application.

It has been found that the addition of Pb may be replaced by an additionof Bi. It has emerged, however, that the addition of Bi leads to hotembrittlement of the brass alloy. Brass alloys of this kind have onlylimited amenability to hot forming. Consequently, such brass alloys arenot used for parts shaped by pressing.

The above-referenced EP 3 320 122 B1 discloses a brass alloy withneither Pb nor Bi added. To improve the machinability, the addition tothe brass alloy of 0.005 to 1.0% In is proposed. The proposed additionof In does indeed improve the machinability. Machining, however,produces relatively long spiral chips, which can lead to blockages asthey are transported away, and to tool breakage.

SUMMARY OF THE INVENTION

It is an object of the invention to eliminate the disadvantagesaccording to the prior art. The intention more particularly is tospecify a brass alloy of improved machinability. According to a furtherobjective of the invention, the brass alloy is to exhibit low hotembrittlement, so allowing it to be processed by hot forming.

This object is achieved by the features of the independent claim.Judicious embodiments are apparent from the features of the dependentclaims.

In accordance with the invention, a brass alloy is proposed with

-   -   54 to 64% Cu,    -   0.15% Al,    -   0.5% In,    -   at least one of the components Fe, Sn and Ni in an amount        collectively of 0.01 to 3.0%,    -   balance Zn and also    -   unavoidable impurities.

For the purposes of the present description, [%] is understood to bepercent by weight.

It has surprisingly emerged that through the addition of 0.05 to 0.15%Al, as proposed in the invention, to a brass alloy which contains 0.005to 0.5% In, improved chip breaking can be achieved. The proposed brassalloy is notable for low hot embrittlement. It may be processed by hotforming.

To produce the proposed brass alloy, neither Pb nor Bi are added. Theaforesaid elements are included in the proposed brass alloy, if at all,only as unavoidable impurities.

According to one advantageous embodiment, at least one of the componentsFe, Sn and Ni is present in an amount of 0.05 to 0.4%, preferably in anamount of 0.1 to 0.3%. With particular preference, the components Fe, Snand Ni are present in an amount of in each case 0.1 to 0.3%. Theproposed addition of Fe and Ni influences the grain growth of the alphaand beta solid solutions. Sn stabilizes the beta solid solution.Accordingly, through the fractions of Fe, Sn and Ni, it is possible toadjust the ratio between the alpha and the beta solid solution orbetween the alpha and beta phases.

According to a further embodiment, the brass alloy contains Si in anamount of up to 0.01%. Si likewise acts to stabilize the beta phase.

According to a further embodiment, Mn is present in an amount of up to0.2%. Mn as well stabilizes the beta phase and with other elementscontributes to the formation of precipitates which have beneficialconsequences for the machining behavior.

It has proven advantageous, furthermore, for the Zn content to be to44%, preferably more than 41% and less than 43%. A brass alloy havingthe proposed Zn content comprises relatively little Cu and isconsequently inexpensive to produce.

According to a further particularly advantageous embodiment, the onlycomponents added for producing the proposed brass alloy are thefollowing: Cu, Fe, Ni, Sn, In, Al and Zn. Accordingly, the followingcomposition has proven particularly advantageous:

-   -   56.0 to 58.0% Cu,    -   to 0.3% Fe,    -   to 0.3% Ni,    -   to 0.3% Sn,    -   0.005 to 0.25% In,    -   0.05 to 0.15% Al,    -   balance Zn and also    -   unavoidable impurities.

The proposed brass alloy is notable for very good machinability. It canbe deformed by hot forming.

The brass alloy advantageously comprises a matrix composed of a betasolid solution with fractions of an alpha solid solution. The fractionof alpha solid solution is advantageously at least 28%, preferably atleast 30%. The proposed brass alloy is notable for particularlyfavorable machine behavior.

The proposed brass alloy may further comprise one or more of thefollowing components.

Sb and/or Cd and/or Se in an amount of in each case up to 0.5%. It hasemerged that higher contents of Sb and/or Cd and/or Se are detrimentalto the properties of the brass alloy.

Ca and/or Mg in an amount of in each case up to 1.0%. Ca and/or Mgcontribute to the formation of precipitates in the solid solution. Suchprecipitates favor the machinability of the brass alloy.

P in an amount of up to 0.1%. P contributes to improve corrosionresistance of the brass alloy. In particular, P counteracts removal ofzinc.

Cr in an amount of up to 0.2%. Cr may in turn contribute to theformation of precipitates in the solid solution that favor themachinability of the brass alloy.

Illustrative examples of the invention are elucidated below.

The table below shows the composition of a reference alloy and also ofan alloy according to the invention.

TABLE I Cu Fe Ni Si Mn Sn In Al Zn Reference alloy 56.51 0 23 0 24 0.030.02 0 26 0 24 — Balance alloy of the invention 56.45 0.19 0.19 0.0010.01 0.21 0.10 0.09 Balance

The numerical values reported in the table above are [%] or [wt %].

The microstructure of the reference alloy consists of a matrix composedof a beta solid solution with 39% alpha solid solution.

The microstructure of the alloy of the invention consists of a matrixcomposed of a beta solid solution with 32% alpha solid solution.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a brass alloy, it is nevertheless not intended to be limited to thedetails shown, since various modifications and structural changes may bemade therein without departing from the spirit of the invention andwithin the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an illustration showing chips after a machining trial on thereference alloy (prior art); and

FIG. 2 is an illustration showing chips after a machining trial with thealloy of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Trial parameters used for performing the machining trials were asfollows:

-   -   Rotary speed n of the spindles: 1600 min-1,    -   Advance velocity f: 0.1 mm/revolution,    -   Cutting depth a: 1.25 mm, and    -   Tool used: indexable cutting insert VBMT 160408-UR.

The machining trials were carried out in each case on specimens havingan identical geometry.

FIG. 1 shows the result of the machining trial using the referencealloy. The chips formed are relatively long spiral chips. Their meanfirst length is approximately in the range from 15 to 20 mm.

FIG. 2 shows the result of the machining trial using the alloy of theinvention. The chips formed are short, broken chips. Their mean secondlength is approximately in the range from 5 to 10 mm.

1. A brass alloy, comprising: 54 to 64 wt % Cu; 0.05 to 0.15 wt % AI;0.005 to 0.5 wt % In; at least one component selected from the groupconsisting of Fe, Sn and Ni in an amount collectively of 0.01 to 3.0 wt%; balance Zn; and unavoidable impurities.
 2. The brass alloy accordingto claim 1, wherein the at least one component selected from the groupconsisting of Fe, Sn and Ni is present in the amount of to 0.4 wt %. 3.The brass alloy according to claim 2, wherein the at least one componentselected from the group consisting of Fe, Sn and Ni is present in theamount of to 0.3 wt %.
 4. The brass alloy according to claim 3, whereineach of Fe, Sn and Ni is present as three components each being presentin an amount of in each case of 0.1 to 0.3 wt %.
 5. The brass alloyaccording to claim 1, further comprising Si in an amount of up to 0.01wt %.
 6. The brass alloy according to claim 1, further comprising Mn inan amount of up to 0.2 wt %.
 7. The brass alloy according to claim 1,wherein the Zn content is 40 to 44 wt %.
 8. The brass alloy according toclaim 1, wherein only the following components have been added: Cu, Fe,Ni, Sn, In, Al and Zn.
 9. The brass alloy according to claim 8, wherein:56.0 to 58.0 wt % Cu; 0.1 to 0.3 wt % Fe; 0.1 to 0.3 wt % Ni; 0.1 to 0.3wt % Sn; 0.005 to 0.25 wt % In; 0.05 to 0.15 wt % AI; balance Zn; andunavoidable impurities.
 10. The brass alloy according to claim 1,further comprising a microstructure having a matrix of a beta solidsolution with fractions of an alpha solid solution.
 11. The brass alloyof claim 10, wherein a fraction of the alpha solid solution is at least28 wt %.
 12. The brass alloy of claim 10, wherein the fraction of thealpha solid solution is at least 30 wt %.
 13. The brass alloy accordingto claim 1, wherein the Zn content is more than 41 wt % and less than 43wt %.